Antimatter trapped for 1,000 seconds

Emma Woollacott, 6th June 2011

CERN scientists have succeeding in trapping antimatter for a record 16 and a half minutes - long enough to begin studying it in detail.

CERN's ALPHA experiment captured 300 atoms of antihydrogen, allowing it to be mapped precisely using laser or microwave spectroscopy and then compared to the hydrogen atom.

"We can keep the antihydrogen atoms trapped for 1,000 seconds,” explained ALPHA spokesperson Jeffrey Hangst of Aarhus University. “This is long enough to begin to study them - even with the small number that we can catch so far."

The team hopes to observe any differences between antihydrogen and hydrogen, as well as measuring the influence of gravity on antimatter with the AEgIS experiment.

It's not the first time scientists have succeeding in trapping antihydrogen. But a big advantage of trapping it for long periods is that the antiatoms have time to relax into their ground state - in which they're more stable and easier to measure more precisely.

This will allow ALPHA to conduct the precision measurements necessary to investigate change-parity-time (CPT) symmetry.

This predicts that a particle moving forward through time in our universe should be indistinguishable from an antiparticle moving backwards through time in a mirror universe, and requires that hydrogen and antihydrogen have identical spectra.

"Any hint of CPT symmetry breaking would require a serious rethink of our understanding of nature," says Hangst. "But half of the universe has gone missing, so some kind of rethink is apparently on the agenda."

ALPHA should start performing measurements on trapped antihydrogen later this year. The first step is to illuminate the trapped anti-atoms with microwaves, to determine if they absorb exactly the same frequencies
as normal hydrogen.

"If you hit the trapped antihydrogen atoms with just the right microwave frequency, they will escape from the trap, and we can detect the annihilation – even for just a single atom," explains Hangst.

"This would provide the first ever look inside the structure of antihydrogen – element number 1 on the anti-periodic table."